N
a, K-ATPase is present in the membrane of most eukaryotic cells and creates trans-membrane gradients of Na and K ions,
which control directly or indirectly essential physiological functions of all animal cells. Regulation of this enzyme and its
isoforms is believed to play a key role in various pathological processes, including cancer. The Na+, K+-ATPase consists of two
subunits,
α
and
β
, in addition to a single membrane-span FXYD regulatory protein. There are four isoforms of
α
(
α
1-4) and
three isoforms of β (β1-3), which are expressed in a tissue-specific fashion. Cardiac glycosides (CG) such as digoxin or ouabain
are specific inhibitors of Na,K-ATPase. CG?s display distinct
in vitro
anti-cancer effects, but the full anti-cancer potential of this
drug has not yet been addressed. In order to improve selectivity and affinity of cardiac glycosides for the different
α
isoforms
of the human Na,K-ATPase we synthesized new digoxin derivatives, modified in the sugar moiety. We have investigated the
effects of CG?s and the digoxin derivatives on cell growth and survival of different human cancer cell lines. The IC50 values for
growth inhibition of human cancer cells
in vitro
are linearly correlated with the number of binding sites of NaK-ATPase and
with the Ki for inhibition of the purified human NaKα1β1 complex. Together, these observations imply that the IC50 values
by the different compounds are a consequence of binding to and inhibition of the pump, andquestion the potential of cardiac
glycoside as selective anti-cancer drugs

Biography

Adriana Katz is an Associate Staff Scientist at the Biological Chemistry department, at Weizmann Institute of Science in Israel, with expertise in membrane proteins,
structure-function and protein interactions. The research mainly involves characterization of membrane transport systems, structure and regulation. She has
specialized in proteomic analysis - 2D gels, Blue native gels, membrane protein separations and identifications by Mass Spectrometry aimed to identify interacting
proteins in the membrane. She is now extending her work to the mammalian Na,K-ATPase including structure-function analyses, inhibition by cardiac glycosides
and drug design. She holds a PhD in Biochemistry from the Hebrew University in Jerusalem